Means for producing integral finned tubing



y 1961 w H. LABAN 2,983,168

MEANS FOR PRODUCING INTEGRAL FINNED TUBING Filed Dec. 31, 1958 3 Sheets-Sheet 1 WILLIAM HENRY LABAN INVENTOR ATTORNEY May 9, 1961 w. H. LABAN MEANS FOR PRODUCING INTEGRAL FINNED TUBING Filed Dec. 31, 1958 3 Sheets-Sheet 2 MmmmmV A b E\\\\\ x FIG. 4.

a? E\\\\ a/ //A WILLIAM HENRY/.ABAN INVENTOR l BYE4 ATTORNEY United States Patent MEANS FOR PRODUCING INTEGRAL FINNED TUBING William Henry Laban, West Hagley, England, assignor to Accles & Pollock Limited, Birmingham, England, a British company Filed Dec. 31, 1958, Ser. No. 784,205

Claims priority, application Great Britain Jan. 6, 1958 3 Claims. (CI. 80-13) This invention relates to means for developing integral fins orr ibs around metal tubes, such means comprising a forming roll or rolls, or a disc assembly or assemblies, having annular operating portions which are caused to exert pressure on a tube to extrude from the wall of the latter on integral fin or rib, or which openate on a partly developed fin, which may be of a helical form, three rolls or disc assemblies being, for example, spaced equi-distantly around a tubular blank, in rolling contact therewith, the axes of the rolls, where the fin is to be of a helical form, being at a slight angle to the axis of the tube, according to the helix angle of the fin which is to be developed.

The object of the invention is to provide a fin developing roll or disc assembly, or a plurality of rolls or disc assemblies, of an improved or novel form which may be used effectively in the later stages of the fin development, and whereby the rubbing and frictional areas of the operative annular portions are reduced, thereby not only preventing roll or disc breakage but also preventing tearing or breaking away of the fin, which is particularly liable to occur when forming very thin fins owing to the axial or lateral pressures which are exerted against the sides of the fin during the later stages of its development. Also, excessive roll wear and high heat and power losses are avoided.

According to the invention, a roll or disc assembly for use in the development of an integral fin around a tube has a plurality of annular parts intended to be brought into rolling contact with the wall of a partly developed fin, the said annular parts being adapted to be brought into operative engagement with a particular part of the fin one after another, to complete, or partly to complete, its formation, the said annular parts, or some of the annular parts, being of a tapering or wedge formation, the wedge angle of an annular part or parts brought into operation at a later stage of the fin development being greater than the wedge angle of a preceding operative annular part or parts.

Throughout the specification and claims the term wedge angle is used to describe the angle formed by the two converging sides of an annular part or portion.

Also, according to the invention, a plurality of fin producing rolls or disc assemblies are spaced around a tube from which a fin is to be developed, or from which a fin has been partly developed, the said rolls or disc assemblies each having a plurality of annular parts spaced apart, in an axialy direction, for rolling contact with the fin, the annular parts of the said rolls or disc assemblies being brought into operative engagement with a particular part of the fin successively, one at a time from each roll in turn, some or all of the annular parts being of a tapering or wedge formation, and the wedge angle of annular parts which are brought into operation on a part of the fin at a later stage in the fin development being greater than the wedge angle of a preceding annular part or parts which has or have already operated ice on that part of the fin. The annular parts may vary in diameter and in thickness, and some may be of a part wedge formation and part parallel sided, instead of being entirely of a wedge form. The annular parts of the rolls or disc assemblies may be divided, in the order of their operation, into groups, those of each succeeding group having a larger wedge angle, and after each wedge angle increase, the first annular part of the next group maybe of a reduced diameter, the diameters of the following annular parts of the same group increasing successively or in stages.

Figure l of the accompanying drawings is a diagrammatic view showing three rolls disposed around a tube for forming a helical fin thereon.

Figure 2 is a longitudinal section through a portion of one of these rolls in accordance with the present invention.

Figure 3 is a similar sectional view of the second roll which acts upon a part of the fin after the first roll has acted upon it, this second roll being formed in accordance with the invention.

Figure 4 is a similar sectional view of the third roll which acts upon a part of the fin after the second roll has acted upon it and which is formed in accordance with the invention.

Figure 5 is a longitudinal section, on a larger scale, of the peripheral portions of the discs which form part of the roll shown in Figure 2.

Figure 6 is a longitudinal section, on a larger scale, of the peripheral portions of the discs which form part of the roll shown in Figure 3.

Figure 7 is a longitudinal section, on a larger scale, of the peripheral portions of the discs which form part of the roll shownin Figure 4.

Referring to the drawings, the means for forming a helical fin 1 around a tube 2 comprises three fin forming rolls A, B and C, spaced equi-distantly around the periphery of the tube which is to be finned, with the axes of the rollsdisposed at a slight angle to the axis of the tube, in known manner, according to the desired helix angle of the fin which is to be produced. Each roll is formed with a plurality of annular parts spaced apart in the axial direction of the roll and arranged to be brought into rolling contact with the tube wall, and, by exerting pressure on the latter, to extrude from the wall a partly formed fin, other annular parts, by acting on the fin, completing its development. Corresponding points on the edges of the commencing ends of the three rolls lie in the same plane, the pitches of the annular parts of the three rolls being the same, but the annular parts of each roll are advanced relatively to the annular parts of the next preceding roll by a fraction of the pitch equal to the reciprocal of the number of rolls, that is, in the present case, the annular parts of the second roll are advanced relatively to the annular parts of the first roll by a distance equal to one third of the pitch of the annular parts, whilst the annular parts of the third roll are advanced relatively to the annular parts of the first roll by a distance equal to two-thirds of the pitch of the annular parts. If, for example, four rolls were employed the annular parts of each roll would be advanced relatively to the annular parts of the next preceding roll by a distance equal to one quarter of the pitch of the annular parts.

Each roll comprises two main parts, namely a primary part for initiating the development of the fin around the tube and a secondary part for deepening and thinning the fin and for finishing its development. The primary part 3 of the roll is of solid form, either in one piece or in two pieces, as shown, with a plurality of integral annular parts or ribs 4, separated by grooves,

parallel sided, but the discs vary in diameter.

around its periphery the said annular parts or ribs being mainly of a square section with flat parallel sides, whilst they increase, excepting for the last three ribs of the series, progressively in diameter providing between them annular parallel-sided grooves of progressively increasing depth, the bottoms of the grooves being of a semicircular section. The three last annular parts of the series maybe of equal or nearly equal diameter, with semi-circular sectioned peripheral edges, instead of being of a square section, whilst the peripheral edges of the commencing annular parts or ribs may be slightly concave. The said primary part 3 of each roll may be formed with any suitable number of annular parts or ribs, and the commencing ribs in particular are of a robust formation and are not liable to break ch in use.

The above-described primary part 3 of each roll is clamped against a collar 5 on an axial shaft 6 by a spacer ring 7 and nut 8 mounted upon the shaft, and the secondary part of the roll is supported on the spacer ring 7. This secondary part is made up of a plurality of loose discs, 9, for example nine, the discs, which are of varying diameters and have annular peripheral parts spaced by grooves and are formed with semi-circular sectioned peripheral edges; The discs are free to turn freely about the spacer ring 7 independently of one another and are driven by the tube 2 around which the fin 1 is to be developed. The annular parts of the disc assemblies of the three rolls A, B and C are, in use, brought into operative engagement with the same part of the partly-developed fin successively, one at a time from each roll in turn, the tube moving axially during the development of the fin, whilst the discs are of a tapering or wedge shape, or partly of a wedge shape and partly parallel sided. The discs, which may or may not vary in thickness, are divided according to their wedge angle into groups distributed over the three rolls, the wedge angle of the annular parts 10 of the discs 9 of each successive group being greater than the wedge angle of the corresponding discs of the next preceding group, the discs of the three rolls being divided, in the present case, into three groups.

After the initial development of the fin by the primary parts 3 of the three rolls the operation of the disc assemblies on a specified part of the fin, as the latter leaves the primary parts of the rolls, is as follows:

The operative annular parts 10 of the first two discs of each of the rolls A, B and C each has a tapering portion with a wedge angle of 3 /2 being either entirely of a tapering form, or partly tapering and partly These 3 /2" rolls are indicated in Figru'es 2 to 7 by the reference letter a.

The first disc of roll A is first brought into rolling en- 7 gagement with the partly developed fin as it leaves the primary part 3 of the roll, and the operative annular part 10 of this disc is entirely of a taper formation. It is, however, of a relatively small diameter, being of a diameter less than that of the last annular part 4 of the primary roll. The said disc thus does not reach to the bottom of the groove between the convolutions of the fin, and merely exerts a lateral wedging pressure against the fin sides, leaving the root portion undisturbed. The fin is thus thinned out and elongated. The first disc of roll B then comes into operation. The operative annular part of this disc is also entirely of a taper formation, but the disc is of a diameter slightly larger than that of the previously mentioned disc of the roll A. It thus reaches further up to the root end of the fin and the metal is extruded from nearer the root end, but the root end itself is still left undisturbed. The first disc of the third roll C, which now comes into operation, is of a still larger diameter, and whilst its outer peripheral portion is of a wedge formation, its inner peripheral part is parallel sided, so that this parallel-sided portion does not operate on the fin sides, but the wedge portion,

on the other hand, operates nearer to'the root end of the fin, although the actual root end itself is still undisturbed. The second disc of roll A is now brought into operative engagement with this particular part of the fin, as it leaves roll C, and this disc is of a still larger diameter so that it reaches still further up to the root end of the fin, but still leaves the extreme root portion undisturbed. The inner periphery of the operative part of this disc is likewise parallel sided and only its outer peripheral portion is of a wedge formation, so that only that part of the fin near to the root is acted upon. The second disc of roll B is again of a still larger diameter to extend right up to the root end of the fin, being of a diameter slightly larger than that of the last annular part 4 of the primary roll 3. Only the outer peripheral part of this disc is of a wedge formation, the remainder being parallel sided, and the disc operates directly on, and deepens, the root end portion of the fin. The second disc of roll C now comes into operation. This disc is of a diameter very slightly less than that of the last-named disc and it is of a taper formation throughout. Whilst it thus serves to hold or support the metal at the extreme root end of the fin, it, at the same time, operates. and slightly compresses the fin sides. The first two discs of the three rolls have now completed the first stage in the tapering of the fin, theprirnary part 3 of the roll having produced only a parallel-sided fin.

The next set of discs are now brought into operation, one at a time from each roll in turn, these discs, which include the third, fourth 'and fifth discs of rolls A and B, and the third and fourth discs of roll C, all having a wedge angle of 6. These 6 discs are indicated in Figures 2 to 7 by the reference letter b. The diameters of these discs also progressively increase in the order of their operation on the fin, excepting for the last two discs, the diameters of which may be slightly decreased in relation to the diameter of the preceding discs. In the order of their engagement with the fin, the first two discs of the 6 series are wholly a taper formation, the next five discs, still in the order of their engagement with the fin, being partly of a taper form and partly parallel sided, only their outer peripheral parts being of a wedge form, and the last disc of the series is wholly of a Wedge formation.

The fin now passes to the next set of discs, commencing With the next disc of roll C, and Which include the last five discs of roll C and the last four discs of rolls A and B, all these discs having a still larger taper namely, a wedge angle of 7%". These 7 Ai discs are indicated in Figures 2 to 7 by the reference letter c. Here again the discs of this last series progressively increase in diameter, in the order of their engagement with the fin,

up to a certain stage in the fin development, the first five discs of the series increasing in diameter in the order of their engagement with the fin. In their order of engagement, the first disc of the. series (the fifth disc of roll C) is of a wholly taper formation. The next six discs are parallel sided, with only their outer peripheral parts of a taper formation, and the last five discs are of a wholly tapering formation. The action of the last two sets of discs (the 6 and 7% sets) in the development of the fin is substantially the same as with the first 3 /2 set of discs, excepting that the Wedge angle increases, exerting a progressive wedging action on the sides of the tin, the partly parallel sided and partly tapering discs acting only on the fin near to, or at, the root end portion of the fin, according to the diameter of the disc, until after all, or most, the discs have been brought into operation the root portion of the fin is finally shaped, the operation of the discs at the same time deepening and thinning the fin. Only a rubbing action against the fin sides occurs at the wedge surfaces of the discs, the parallel portions of the latter being inoperative on the fin, and in thi way friction is kept to a minimum, and is present only at those parts of the fin where it is most needed for the proper development of the latter. As the tapering surfam of the discs, and their contact with the fin, are at difierent distances from the shaft by which they are supported, the discs rotate independently on the shaft at different speeds, and being loosely mounted on the shaft they-position themselves correctly in relation to the fin, a slight clearance being left between the end face of the first discs of each roll and the opposed end face of the primary part of the roll, as indicated in Figures 5 to 7.

Each roll may have any number of sets of loosely mounted discs, the discs of difierent sets having different wedge angles, so that the discs with the larger wedge angle are brought into operation at a later stage in the fin development. The wedge angles may be varied as desired, and the diameters of the discs of each roll may be varied, as found most suitable for the fin which is being developed; also the number of discs whose outer peripheral parts are wholly of a wedge formation, and those whose outer peripheral parts are partly of a wedge formation and partly parallel sided, may be varied as found mo'st suitable. The thickness of the operative portions of the discs may also vary, and any number of rolls may be employed.

I claim:

1. Means for developing a helical fin upon a tube, said means comprising a plurality of roll units adapted to be spaced around the tube, each unit comprising the combination of a positively-driven primary portion initiating the development of the fin and comprising a member having annular ribs separated by grooves, with a secondary portion for finishing the fin and consisting of a plurality of loosely-mounted freely and independently rotatable floating discs free to be rotated by the tube relatively to the said primary portion, said discs having wedge-shaped annular portions, the annular portions of the discs of the several roll units being adapted to be brought into engagement with a part of the fin successively, one at a time, from each roll unit in turn, and divided into groups distributed over the roll units and having difierent wedge angles, the wedge angle of one group being greater than the wedge angle of another group that is brought into operation at an earlier stage, the diameters of the annular portions in each group being of progressively increasing diameter in the order of their operation on the fin.

2. Means for developing a helical fin on a tube, according to claim 1, wherein the first annular portion of each group is of a reduced diameter in relatio'n to that of the last annular portion of the next preceding group.

3. Means for developing a helical fin on a tube, said means comprising a plurality of roll units adapted to be spaced around the tube, each unit including a fin-finishing portion consisting of a plurality of adjacently-disposed and independently rotatable loose discs divided into groups, each disc having an outer annular portion of wedge-section, adjacent groups of said discs having annular portions of different wedge angle, annular portions in one group having a larger Wedge angle than annular portions of a preceding group, considered in the order of their operation, and the discs in each group being of progressively increasing diameter in their order of operation.

References Cited in the file of this patent UNITED STATES PATENTS 

